The present invention relates to an apparatus for fitting containers with caps. More particularly, it is directed to a novel capping machine capable to deposit a cap on a container neck such that the cap is aligned with the container neck.
In the bottling industry, reclosable containers are usually sealed with screw-type caps. To achieve a high productivity, the container sealing operation is performed by automatic capping machines processing in succession the containers transported in serial order on a conveyor belt or any other type of materials handling machine. In typical capping machines, the container sealing operation is a two-step process. Firstly, the open container passes underneath a cap dispensing station applying loosely on the container neck a screw-type cap in thread alignment with the threads on the container neck. For the purpose of this specification, the term xe2x80x9cthread alignmentxe2x80x9d designates a condition where the cap is not threadedly engaged on the container neck, however the threads on the cap and on the neck respectively are so disposed that rotation of the cap will cause the threads to mate in the correct fashion, resulting in thread engagement. In contrast, the term xe2x80x9cthread misalignmentxe2x80x9d will be used to identify a condition where rotation of the cap will cause improper thread engagement resulting in a poorly sealed container. The container is then transported to a cap tightening station where a chuck rotatably grips the cap, tightening it and sealing the container.
The accurate positioning of the cap on the container neck is an important operation to ensure a proper thread engagement during the cap tightening stage. Existing capping machines use a simple method to deposit the caps on the containers at the cap dispensing station. The caps are fed from a supply chamber or magazine to a cap-dropping aperture where a latch drops the caps on the containers in a timed relationship with the container feed rate. Unfortunately, although a cap is dropped only a very short distance from the top of a container neck, during its free fall the cap may tilt slightly, landing in an improper position on the container and failing to produce the desired thread alignment condition. Deep caps or caps with large threads have inherent self-centering capability and, accordingly, they can compensate, to a certain extent, for an imprecise positioning. However, shallow caps and caps with smaller thread sizes, have little ability to self-center themselves, in which case an improperly positioned cap will fail to produce a correct thread engagement during the cap tightening operation, resulting in a poorly sealed container.
In U.S. Pat. No. 5,115,617, issued on May 26, 1992 to H. G. Kalish Inc., a capping machine is disclosed in which the cap dispensing station includes a cap-dropping aperture partially closed by a resilient lip. This lip prevents a cap from travelling through the cap-dropping aperture. The cap dispensing station further includes a selectively actuatable cap ejector that drives the cap through the cap-dropping aperture against the resiliency of the lip, freeing the cap for deposit onto the container neck. Frictional engagement between the resilient lip and the cap during its movement through the cap-dropping aperture guides the cap such that it is precisely positioned on the container. Unfortunately, a weakness of this design is the wear suffered by the resilient lip over time, which causes the opening in the lip to become too large such that the lip can no longer hold a cap properly in place. Further, during movement of the cap through the cap-dropping aperture, the downward motion of the resilient lip may permit a tilting of the cap, resulting in a thread misalignment condition between the cap and the container neck.
The background information provided above clearly indicates that there exists a need in the industry to provide an improved mechanism for applying caps onto container necks within capping machines, such that accurate cap positioning is repeatedly achieved.
The present invention provides in one aspect an apparatus for capping in succession containers transported on a conveyance device. The apparatus includes a cap dispensing station for applying on each container a cap. The cap dispensing station includes a gating unit that controls the movement of a cap through a cap release passage. When the cap is allowed to travel through the cap release passage it is deposited onto a container underneath. The gating unit includes a barrier associated to the cap release passage, and a barrier drive mechanism associated to the barrier. In a first operative position, the barrier at least partially closes the cap release passage to prevent a cap from freely traveling through the passage under the effect of gravity. In a second operative position, the barrier uncovers the cap release passage to allow a cap to travel through the passage. The apparatus also comprises a movable cap ejector that engages the barrier drive mechanism such that the barrier drive mechanism causes the barrier to acquire the second operative position.
The capping apparatus as described above yields the benefit of repeatable accurate cap dispensing over containers to be capped, by virtue of the novel gating unit.
In a specific non-limiting example of implementation, the barrier drive mechanism of the gating unit includes a pair of arms slidingly mounted on tracks. The spacial position of the arms is such that they extend in the path of travel of the cap ejector. When the cap ejector moves toward the arms it engages the arms and causes the arms to move on the tracks. The arms are mounted to the barrier such that the movement of the arms causes the barrier to acquire the second operative position in which the cap release passage is uncovered. In particular, the barrier has a pair of portions, each portion mounted to a respective arm. Each barrier portion moves with the respective arm so as to uncover the cap release passage. When the cap has been deposited on the container, the cap ejector is withdrawn. The arms are spring-loaded and they move back to their initial rest position, causing the barrier portions also to move back to the first operative position, at least partially closing the cap release passage to prevent a cap from passing through the passage.
In a second broad aspect, the invention provides a capping machine including a cap ejector that can grasp the cap and transport the cap toward the container to be capped. Thus feature is advantageous in that the movement of the cap toward the container is well controlled which translates in a more accurate cap dispensing operation.
In a non-limiting example of implementation under the second broad aspect, the cap ejector includes a gripping device that engages and holds the cap, preventing it from moving freely under the effect of gravity. The cap ejector moves toward the container to carry the cap and deposit the cap on the container neck. When the cap ejector has reached the container neck it releases the cap such that the cap rests on the container neck, allowing the cap ejector to withdraw. In a specific non-limiting example of implementation, the gripping device includes a recess at the base of the cap ejector, dimensioned for receiving at least a portion of a cap. A fluid communication channel connected to a source of vacuum terminates in the recess to selectively establish a pressure differential therein. The pressure differential holds the cap in the recess against the force of gravity. The cap ejector then moves toward the container, transporting the cap with it. The pressure differential is terminated once the cap ejector has reached the container, allowing the cap to be released from the cap ejector.
In a possible variant, a motor in driving relationship with the cap ejector imparts a rotational movement to the cap ejector for threadedly engaging and tightening the cap on the container neck.